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@ARTICLE{Volmer:1049183,
      author       = {Volmer, Mats and Struck, Tom and Tu, Jhih-Sian and
                      Trellenkamp, Stefan and Esposti, Davide Degli and Scappucci,
                      Giordano and Cywiński, Łukasz and Bluhm, Hendrik and
                      Schreiber, Lars R.},
      title        = {{R}eduction of the impact of the local valley splitting on
                      the coherence of conveyor-belt spin shuttling in
                      $^{28}${S}i/{S}i{G}e},
      publisher    = {arXiv},
      reportid     = {FZJ-2025-05266},
      year         = {2025},
      abstract     = {Silicon quantum chips offer a promising path toward
                      scalable, fault-tolerant quantum computing, with the
                      potential to host millions of qubits. However, scaling up
                      dense quantum-dot arrays and enabling qubit interconnections
                      through shuttling are hindered by uncontrolled lateral
                      variations of the valley splitting energy $E_{VS}$. We map
                      $E_{VS}$ across a $40 \, $nm x $400 \, $nm region of a
                      $^{28}$Si/Si$_{0.7}$Ge$_{0.3}$ shuttle device and analyze
                      the spin coherence of a single electron spin transported by
                      conveyor-belt shuttling. We observe that the $E_{VS}$ varies
                      over a wide range from $1.5 \, μ$eV to $200 \, μ$eV and is
                      dominated by SiGe alloy disorder. In regions of low $E_{VS}$
                      and at spin-valley resonances, spin coherence is reduced and
                      its dependence on shuttle velocity matches predictions.
                      Rapid and frequent traversal of low-$E_{VS}$ regions induces
                      a regime of enhanced spin coherence explained by motional
                      narrowing. By selecting shuttle trajectories that avoid
                      problematic areas on the $E_{VS}$ map, we achieve transport
                      over tens of microns with coherence limited only by the
                      coupling to a static electron spin entangled with the mobile
                      qubit. Our results provide experimental confirmation of the
                      theory of spin-decoherence of mobile electron spin-qubits
                      and present practical strategies to integrate conveyor-mode
                      qubit shuttling into silicon quantum chips.},
      keywords     = {Quantum Physics (quant-ph) (Other) / FOS: Physical sciences
                      (Other)},
      cin          = {PGI-11},
      cid          = {I:(DE-Juel1)PGI-11-20170113},
      pnm          = {5221 - Advanced Solid-State Qubits and Qubit Systems
                      (POF4-522)},
      pid          = {G:(DE-HGF)POF4-5221},
      typ          = {PUB:(DE-HGF)25},
      doi          = {10.48550/ARXIV.2510.03773},
      url          = {https://juser.fz-juelich.de/record/1049183},
}